Many Colors Pvc Yoga Mat,Pvc Yoga Mats,Yoga Mat,Customized Yoga Mat Anyang Qunxiu Plastics co.,ltd , https://www.qunxu.com
For someone who has never had experience wiring I/O for motion control, it can be quite intimidating at first. If devices are not wired correctly, it can lead to a range of problems, from a motor not functioning as expected to even irreversible damage to the equipment. I still get that nervous feeling before pressing the START button on a demo. Murphy's Law, anyone?
The confusion often starts when engineers or manufacturers use different wiring terminology. How can you be sure that you're comparing similar concepts? For example, is sourcing logic the same as PNP logic? "Are we sinking or taking a sinked source?" In our experience supporting motion control applications, we've heard all sorts of variations.
Most of the time, tech support engineers will direct you to a wiring diagram and advise you to follow it. But what exactly do terms like sink logic and source logic mean? Let’s start with some basic definitions.
**Electronic Circuit (Digital)**
An electronic circuit consists of components such as resistors, transistors, capacitors, inductors, and/or diodes. These are connected by conductive wires or traces on a PCB. It requires a voltage and ground, where ground acts as a reference point to measure potential voltage. A digital electronic circuit uses DC voltage and discrete values (on/off). A DC power source flows from positive to negative.
**I/O**
I/O stands for inputs/outputs, which in simple terms, refers to any device that executes an output based on an input. It could be a keyboard (input) and a monitor (output). In this context, I/O describes signal communication between two devices, such as a PLC and a stepper driver, using on/off binary logic.
**Electrical Load**
An electrical load is a component or part of a circuit that consumes electric power. This is the opposite of a power source, such as a battery or generator, which produces power. Examples of loads include light bulbs and motors. In this case, we're focusing on an input circuit.
**Logic Circuit**
A logic circuit is an electric circuit (I/O) whose output depends on the input. It can include one or more binary inputs (on/off) and a single binary output. It can consist of any binary electric or electronic devices, including switches, relays, solid-state diodes, and transistors.
**Sink Logic vs Source Logic**
Sink and source logic circuits are commonly associated with PLC I/O signals and apply only to DC circuits. They differ based on the type of component used and define the direction of current flow.
- Logic is defined by the type of components in the circuit.
- Logic defines current flow in the circuit.
- Whatever logic you use for the output, the opposite is required for the input.
**Sink Logic**
In a sink logic configuration, an NPN transistor provides a path to ground for the electrical load. For an NPN transistor circuit to work, it must be connected to a PNP transistor circuit. In other words, a sink logic circuit needs to be connected to a source logic circuit.
Figure 1 shows a sinking digital output connected to a sourcing digital input. The input circuit is connected between the positive power supply side (Vcc) and the NPN transistor.
**Source Logic**
In a source logic configuration, a PNP transistor provides a path to voltage for the electrical load. For a PNP transistor circuit to work, it must be connected to an NPN transistor circuit. In other words, a source logic circuit needs to be connected to a sink logic circuit.
Figure 2 shows a sourcing digital output connected to a sinking digital input. The input circuit is connected between the PNP transistor and the power supply GND (0v).
A useful mnemonic trick for sink vs source logic is to think of a source logic circuit as the voltage source (it provides a path to the source), and a sink logic circuit as sinking towards the ground (it provides a path to ground).
**Tip: Compare Wiring Diagrams Side by Side**
When dealing with wiring I/O between a PLC and a servo or stepper driver, a helpful trick that has worked for me is to print out the wiring diagrams from both the PLC and the driver, then place them side by side. This helps visualize the current flow from the voltage source to the load and back to ground.
**Trace the Current Flow**
Many of my support calls were done remotely over the phone, making wiring support challenging. To ensure I didn’t damage my customers' PLCs, I used to print the wiring diagrams and trace the current flow from the voltage source, through the electrical load, and all the way to ground. Supporting remotely also taught me the importance of knowing exactly which side of the I/O the customer was referring to.
For a PLC sourcing output to trigger a sinking input on the driver, we need to make sure everything has the power it needs. Sufficient voltage and current must enter the positive terminal from the PLC side, pass through the output circuit, reach the input circuit (electric load), and exit through another terminal back to the ground of the power supply to complete the circuit. On a PLC, each individual I/O signal should provide two terminals for connection: one for current going in, and one for going out. Sometimes, terminals are grouped together and called "common." This "common" could either be the voltage source or ground.
**Tip: Don't Forget Power Requirements for I/O**
It's also important to pay attention to voltage and current requirements for both inputs and outputs. If the output calls for current-limiting resistors, use Ohm's Law to calculate your external resistance, but don’t forget about the internal resistance. Remember that you have to meet both the voltage and current requirement of the input.
**Which is Safer?**
It's crucial to understand the type of logic or transistor being used to determine the correct wiring method. Additionally, there is a difference in safety. If something goes wrong with the customer's device and causes an I/O signal line earth leakage or short circuit of the ground (0v) line, it could be potentially dangerous.
However, if source logic is used, the input circuit is not directly connected to the positive power side (Vcc), so earth leakage or a short circuit of a signal line would not turn the input on. That’s why it's considered one of the safer connection methods.
**Summary**
Sink and source are terms used to describe the flow of direct current in an electric circuit.
- A sinking input or output circuit provides a path to ground for the electric load.
- A sourcing input or output provides the voltage source for the electric load.
Logic is defined by the type of components in the circuit.
- A sourcing input or output circuit requires a PNP transistor.
- A sinking input or output circuit requires an NPN transistor.
A simple electronic circuit consists of one digital input connected to a digital output. To power the circuit, a voltage source, a ground, and a load are necessary.
- A sourcing input or output circuit provides the necessary voltage for the circuit.
- A sinking input or output circuit provides the necessary ground for the circuit.
- The digital I/O provides the electrical load required for the circuit to function.
**For Flexibility, Use Products That Offer Both Sink and Source Logic**
Certain products in the market offer both sink and source logic for flexibility in connections. This is made possible by bidirectional diodes wired in parallel. Photo couplers also help minimize wiring damages. Use these products if flexibility is desired or if you plan to repurpose them later.
Here's what the actual wiring diagrams look like for the BLE2 Series brushless motor drivers. There is one diagram for connecting sink logic outputs and another for source logic outputs. The PLC, or "Programmable Controller," is on the left, and the motor driver is on the right. The INx designations are inputs, and the OUTx designations are outputs.
Take a look at the first input "IN-COM0" (Inputs Common). On the top wiring diagram, it's connected to 24 VDC, and the input has a path to ground. On the bottom diagram, the "IN-COM0" is connected to 0v, and the input has a path to the voltage source. The bidirectional diodes in the input circuits allow this.
We hope this explanation helps. Most of our newer drivers offer both sink and source logic. If you need assistance locating them, please reach out to our helpful technical support engineers.
If you found this information useful, feel free to subscribe for more updates!